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<H2>ASST8  Assembler</H2>

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<H4><B><PRE>
ST8 REGISTER SET 

The following is a list of the ST8 registers used by ASST8:  

        a       -       8-bit accumulator
        xl,yl   -       LSB of index registers
        xh,yh   -       MSB of index registers
        x,y     -       16-Bit index registers
        sp      -       16-bit stack pointer
        cc      -       8-bit condition code register


ST8 INSTRUCTION SET 


     The following list specifies the format for each addressing
mode supported by ASST8:  

        reg             register addressing
                        (a,x,xl,xh,y,yl,yh,sp,cc)

        #data           immediate data

        *saddr          8-bit zero page addressing
                        0x00 <= saddr <= 0xFF

        laddr           16-bit addressing
                        0x0000 <= laddr <= 0xFFFF

        eaddr           24-bit addressing
                        0x000000 <= eaddr <= 0xFFFFFF

        (x)             register indirect addressing


        (*sofst,r)      short indexed (r = x,y,sp)
        (sofst,r).b

        (lofst,r).w     long indexed (r = x,y)

        (eofst,r).e     extended indexed (r = x,y)
                        eofst is a lofst value,
                        i.e. a 16-bit value where
                        (eofst,r).e points to a
                        24-bit address

        (ofst,r)        for the ldf instruction the
                        (eofst,r).e mode is selected
                        else

        (ofst,r)        if ofst is relocatable or
                        an external value then
                        the (lofst,r).w mode is
                        selected by default
                        else

        (ofst,r)        if ofst is a locally
                        defined constant then
                        the (sofst,r).b mode
                        is selected when
                        0x00 <= ofst <= 0xFF else
                        the (lofst,r).w mode
                        is selected

                        Instructions supporting
                        only a single form will
                        use the appropriate form
                        but will report an error.


        [*saddr]        short indirect
        [saddr].b

        [laddr].w       long indexed

        [eaddr].e       extended indexed

        [addr]          for the callf, jpf, and ldf
                        instructions the [eaddr].e
                        mode is selected
                        else

        [addr]          if addr is relocatable or
                        an external value then
                        the [laddr].w mode is
                        selected by default
                        else

        [addr]          if addr is a locally
                        defined constant then
                        the [saddr].b mode
                        is selected when
                        0x00 <= addr <= 0xFF else
                        the [laddr].w mode
                        is selected

                        Instructions supporting
                        only a single form will
                        use the appropriate form
                        but will report an error.


        ([*saddr],r)    short indirect indexed
        ([saddr].b,r)   (r = x,y)
        ([saddr],r).b

        ([laddr].w,r)   long indirect indexed
        ([laddr],r).w   (r = x,y)

        ([eaddr].e,r)   extended indirect indexed
        ([eaddr],r).e   (r = x,y)

        ([addr],r)      for the ldf instruction the
                        ([eaddr],r).e mode is selected
                        else

        ([addr],r)      if addr is relocatable or
                        an external value then
                        the ([laddr],r).w mode is
                        selected by default
                        else

        ([addr],r)      if addr is a locally
                        defined constant then
                        the ([saddr],r).b mode
                        is selected when
                        0x00 <= addr <= 0xFF else
                        the ([laddr],r).w mode
                        is selected

                        Instructions supporting
                        only a single form will
                        use the appropriate form
                        but will report an error.


        label           pc-relative branch addressing



The  terms data, saddr, laddr, eaddr, addr, sofst, lofst, eofst,
ofst, and label may all be expressions.  

     Note that not all addressing modes are valid with every in-
struction, refer to the ST8 technical data for valid modes.  
The  following  tables  list all ST8 mnemonics recognized by the
ASST8 assembler.  The designation [] refers to  a  required  ad-
dressing mode argument.  


Inherent Instructions 

        nop                     trap
        wfi                     wfi
        halt                    ret
        retf                    iret
        sim                     rim
        scf                     rcf
        rvf                     ccf


Conditional Branch Instructions 

        jra     label
        jrt     label           jrf     label
        jrugt   label           jrule   label
        jruge   label           jrult   label
        jrnc    label           jrc     label
        jrne    label           jreq    label
        jrnv    label           jrv     label
        jrpl    label           jrmi    label
        jrsgt   label           jrsle   label
        jrsge   label           jrslt   label
        jrnh    label           jrh     label
        jrnm    label           jrm     label
        jril    label           jrih    label


Bit Test and Branch Instructions 

        btjt    laddr,#,label
        btjf    laddr,#,label


Bit Manipulation Instructions 

        bccm    laddr,#
        bcpl    laddr,#
        bset    laddr,#
        bres    laddr,#


Single Operand Instructions 

        neg     []              cpl     []
        srl     []              rrc     []
        sra     []              rlc     []
        sll     []              sla     []
        dec     []              inc     []
        tnz     []              swap    []
        clr     []

        negw    reg             cplw    reg
        srlw    reg             rrcw    reg
        sraw    reg             rlcw    reg
        sllw    reg             slaw    reg
        decw    reg             incw    reg
        tnzw    reg             swapw   reg
        clrw    reg

        pop     reg             push    reg


Double Operand Instructions 

        add     a,[]            adc     a,[]
        and     a,[]            bcp     a,[]
        cp      a,[]            or      a,[]
        sbc     a,[]            sub     a,[]
        xor     a,[]

        add     sp,#            sub     sp,#

        addw    reg,[]          subw    reg,[]
        cpw     reg,[]

        mul     x,a             mul     y,a
        div     x,a             div     y,a
        divw    x,y

        exg     a,reg           exg     a,laddr
        exgw    x,y

        rrwa    x,a             rrwa    y,a
        rlwa    x,a             rlwa    y,a

        ld      [],[]
        ldf     a,[]            ldf     [],a
        ldw     reg,[]          ldw     [],reg

        mov     saddr,saddr
        mov     laddr,laddr     mov     laddr,#


Call to Subroutine and Jump Instructions 

        call    []              jp      []
        callf   eaddr           callf   [eaddr].e
        jpf     eaddr           jpf     [eaddr].e

        callr   label

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<H6><P><B>Last Updated: October 2010</B></P></H6>
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